System for elevating building components



Aug. 17, 1965 M. LONG SYSTEM FOR ELEVATING BUILDING COMPONENTS Filed Nov. 13, 1961 5 Sheets-Sheet l g g v. Q:

Aug. 17, 1965 M. LONG SYSTEM FOR ELEVATING BUILDING COMPONENTS Filed Nov. 13. 1961 5 Sheets-Sheet 2 lslgl lswq l- I i 0 V a 3 R OJ Y 0 mm W7 m H T Y B W) Aug. 17, 1965 M.- LONG 3,201,088

SYSTEM FOR ELEVATING BUILDING COMPONENTS Filed Nov. 13. 1961 5 Sheets-Sheet 3 3 i 202 202/90 w w M4 w M w w 1&2 1

w w 02 m 152 0 INVENTOR. 2/5 204 mars/2a Long Aug. 17, 1965 M. LONG SYSTEM FOR ELEVATING BUILDING COMP Filed NOV. 13, 1961 I ill-m (QW P @Wa l l omszm's 5 Sheets-Sheet 4 INVENTOR. Marsha/I Lang Aug. 17, 1965 M. LONG SYSTEM FOR ELEVATING BUILDING COMPONENTS Filed Nov. 13. 1961 5 Sheets-Sheet 5 l wk riJ 0 H 2 w 0 m W h S w J W t a m .9 V

4 5 1 0 0w 1 Z F United States Patent This invention relates to lifting structure including a jack unit for elevating building components, the primary object being to improve upon the teachings of US. Letters Patent No. 2,720,017.

It will be readily appreciated from said patent, that because of the necessity of having a large number of jacks,

it is extremely important that each jack be synchronized with all other jacks of the system to that no intolerable stresses will be applied to the concrete slab as it is being hoisted into place.

While the principles of such patent have been successfully followed for a number of years, and the large numbers of buildings constructed throughout the world in accordance with the novel methods and apparatus therein disclosed, synchronization such as to maintain the slabs level and undeflected has remained somewhat of a problem. Heretofore, the lifting of building slabs has been conventionally carried out by utilizing a plurality of jacks, each of which was supplied with hydraulic fluid through its own separate line communicating with a common source. The amount of load displacement during the lift stroke for these jacks was relatively large, usually amounting to three inches. Any attempt to synchronize the jacks so that the load was displaced uniformly over its entire area, had to be done during the stroke of the jack and was carried out by adjusting the rate of flow of hydraulic fluid to the individual jacks. To this end, each jack was provided with a manual adjusting valve and a counter geared to reflect the linear displacement of the load. By careful attention to the counter readings of all of the jacks and by making adjustments to the valve during the lift stroke itself, it was possible, although difficult, for the operator or operators to maintain the slab substantially undefiected during its lift. It was of extreme importance that such uniformity be maintained because failure of one or more jacks to lift while the others lifted up to three inches could, and likely would, result in deflecting the slab in a manner to cause severe damage thereto. Apparatus of the kind described obviously required a great deal of operator attention and was hazardous to operate.

The system for lifting building components which is the subject of this invention, discards the method of lifting the slabs by relatively large increments during which the jacks are individually adjusted and utilizes instead, the method of limiting the stroke of the jacks to a relatively small amount without attempting to adjust the jacks during the stroke. By selecting the stroke length within the limits of deflection tolerable by the material being lifted, it is possible to safely ignore the jacks during each stroke and make whatever adjustments are necessary following the completion of a particular stroke. If each jack displaces its load the proper amount in the lift stroke, no such adjustment is necessary and the lifting continues automatically in relatively short increments until it reaches the desired location. Since the stroke length is within the deflection tolerance limits of the material, it is then immaterial whether or not the jacks are in precisely the same phase of lift throughout any given stroke. One jack may completely finish its stroke before others have begun to displace the load and no damage will result to the slab. Thus, the jacks may be connected in parallel to a common hydraulic line and the unequal pressures which result, will be of no consequence.

Accordingly, it is the most important object of this invention to provide a system and apparatus for lifting building components wherein the successive increments of lift are each within the tolerable flexure limits of the material being lifted, thereby rendering whatever differences of lift that may occur between the various jacks of the system, incapable of damaging the lifted. material.

A further important object of this invention is to provide a system for lifting building components which utilizes equipment which need not be synchronized within any given lifting stroke.

Still a further object of the instant invention is to provide apparatus for such lifting operations, which apparatus automatically cycles in successive increments so long as the differential of lift between any two jacks of the system does not exceed a certain predetermined amount, and which, if such amount is exceeded, automatically renders the system inoperative.

Another highly important object of my invention is the provision of apparatus whereby very heavy loads may safely be lifted with very little operator attention being required.

Still a further important object of this invention is to provide a system of jack units for lifting a heavy load by increments with each unit provided with a tolerance to compensate for predictable variations in load displacement, yet with each unit capable of automatically rendering the system inoperative upon its failure to advance the load a predetermined distance.

Yet another object of my invention, is to provide in each unit a signaling assembly which will automatically indicate that it has failed to displace its load and has rendered the system inoperative.

A further important object of the instant invention is to provide jack units which may be quickly and easily adjusted and returned to operation after the cause for stoppage is removed.

Another important object of this invention is to provide a system wherein a large number of individual jack units may be safely and successfully controlled simultaneously and essentially without individual operator attention.

A further object of the present invention is to provide each jack with a single prime mover capable of being operated only in predetermined phase relationship with the lifting structure of the jack unit.

A still further object of this invention is the provision of means for selectively delaying the reversal of flow of hydraulic fluid in the system following an indication that all jacks have displaced a proper amount so that even the last jack may utilize maximum pressure build-up for lifting the last small increment of its requisite displacement.

In the drawings:

FIGURE 1 is a front elevational view of a jack unit forming a part of a system for elevating building components made pursuant to my present invention, illustrating fragmentarily a pair of screws with which the jack unit is coupled;

FIG. 2 is a top plan view showing said screws in cross section and with parts broken away for clearness;

FIG. 3 is a fragmentary, cross-sectional view taken along line 33 of FIG. 1;

FIG. 4 is a fragmentary, cross-sectional view taken along irregular line 4-4 of FIG. 2;

FIG. 5 is an enlarged, fragmentary, detailed, crosssectional view taken along line 5-5 of FIG. 4 with parts broken away to reveal details of construction;

FIG. 6 is an enlarged, horizontal, cross-sectional view through the prime mover shown in FIGS. 1 and 4, one of which is provided for each jack unit;

FIG. 7 is an enlarged, elevational view of one of the socket assemblies shown in FIG. 1, with parts broken away for clearness;

FIG. 8 is an enlarged, fragmentary, detailed, cross-sectional view taken substantially along line 88 of F IG. 4;

FIG. 9 is a reduced, fragmentary, rear elevational view on a reduced scale, showing the jack'unit of FIG. 1 mounted on a support;

FIG. 10 is an electro-hydraulic schematic view of the system; and

FIGS. 11 through 16 are diagrammatical views showing relative positions of components at various stages of operation.

The disclosure of US. Patent No. 2,720,017 is incorporated herein by reference as may be needed for a full and complete understanding of the broad principles of the in vention about to be described.

In order to simplify the description, one jack unit broadly designated 20, will be described in detail and includes as basic components, a generally horizontal, elongated, lower head 22, an elongated, upper head 24, and power means broadly designated 26 between heads 22 and 24 and maintaining the same in vertically spaced relationship. As is evident from FIG. 9, the jack unit Zll is adapted to be mounted on the upper end of a vertical column 25 with head 24 carried by such column. The head 22 has a pair of opposed, elongated, parallel surfaces 27 thereon having a series of tapped openings 29 therein for receiving suitable fasteners operating to secure a bracket to the lower part of head 22. The brackets secured to head 27,, maintain the jack 20 in a predetermined position on top of the column 25.

Power means 26 includes a cylinder 23 secured to and carried by head 22, projecting upwardly from the top surface thereof and reciprocably receiving a piston 3%? having a horizontal rib on the upper face thereof which is of convex configuration in transverse cross section and adapted to be complementally received within a groove 32 in the lower surface of head 24.

.Heads 22 and 24 which are preferably in the nature of relatively heavy castings capable of supporting a relatively large load, have vertically aligned, elongated slots 34 and 36 in opposite ends thereof for clearing respective elongated screws 38 and 40 which extend therethrough and are normally disposed in vertical, parallel relationship. The upper. head 24 which is triangular in vertical section, has a pair of opposed, upwardly facing recesses 4-2 therein, aligned with slots 34 and as in head 24 and provided with lower, horizontal, substantially coplanar surfaces 44 in surrounding relationship to the proximal slots 3 and 36.

The head 22 also has upwardly facing flat surfaces in surrounding relationship to the slots 34 and 36 therethrough with the surfaces 4-4 on head 24, as well as the flat surfaces on head 22 serving to slidably support generally rectangular washers 4-6 slidable thereon and provided with openings therethrough for clearing screws 33 and dll respectively. Polygonal nuts 48 and d overlie the washers 46 on head 24 and are complementally threaded over screws 38 and 40, while another pair of nutsBZ and 54 are positioned over the Washers 46 on head 22 and are also threaded over head 22 above the washers 46 thereon. Although not illustrated in the drawings, it is to be recognized that the lower extremities of screws 3% and 4d are suitably anchored or otherwise secured to the slab which is to be lifted by jack unit 20. Each nut 53 to 54 inclusive, is

preferably of split construction and hingedly interconnected on one side thereof so that the nuts may be coupled to screws 38 and 40 at any point along the longitudinal length thereof.

A generally U-shaped bracket broadly designated 56, is secured to the face 58 of upper head 24 and includes a pair of parallel, outwardly projecting, normally horizontal plate portions so and 62 having vertically aligned openings 6.4 therein for rotatably receiving an elongated, vertical shaft 66 which projects outwardly from plate portions es CIl and 62 as best shown in FIG. 4. An enlarged segment 68 on shaft 66, bears against the upwardly extending integral boss '70 on the inner face of plate portion 62, while pinion 72 on shaft d6 above segment 68, is positioned to intermesh with a pinion 74 between plate portions so and 62 and carried by a shaft 76 extending downwardly through plate portion 62 into the housing of a hydraulic motor broadly denominated 86, and carried beneath plate portion 62 by the latter.

As illustrated in FIG. 6, the housing 78 of motor St) is of generally rectangular configuration and includes a pair of horizontal, parallel passages 82 and 8 5 therethrough and which are normally closed at opposed ends thereof by end sections and 88 coupled to opposed extremities of housing 78. The central portion of housing '78 is provided with bore 9%? tn-erethrough clearing shaft in, as well as a pinion 92 thereon within housing 78 and positioned to operably intermesh with the rack portions 9 of pistons 96 and 93 within passages 32 and in housing F8. The opposed extremities Km and u, as well as the extremities 9" and @Sb of pistons 9.; and 98, are of generally cylind ical configuration of slightly less diameter than respective passages and 84, and O-rings litltl are provided around each of the extremities $612, 96b, 98a and $3) of pistons and in slidable, liquid-sealing engagement with the walls of passages 82 and 3d. The central sections of pistons 9-6 and 93 are cutaway through a portion of the longitudinal length thereof in order to clear pinion 92 with the rack portions 94 thereon, thereby extending substantially the full length of the cutaway portions of pistons as and as set forth above.

The end section of motor has a pair of bores M2 and l l l therein communicating with the passages 32 and 8 2- respectively, while generally frusto-conical, threaded passages ltid and 1&8 are aligned with and communicate with the bores and lu l respectively. Hydraulic lines for supplying fluid under pressure to housing "'78 will be explained in greater detail hereinafter. The end section on housing '78 is also provided with bores 11% and 132 therein communicating with the passages 82. and 3d respectively, while longitudinally extending cross passage 114 intercommunicates bore M 2 and bore 112, and another cross passage 116 couples bore 1-34 with bore Another generally U-shapcd bracket 1. g is secured to head 22 immediately below bracket 56 on head 22, and has a pair of outwardly projecting, horizontal, vertically spaced plate portions 119 and 121 provided with aligned openings 12% therein for receiving a sleeve 122, which in turn carries a bearing 12%. Bearing 124 within sleeve 122, extending upwardly therefrom, serves to rotatably carry an elongated siaft us which projects upwardh from the upper extremity of bearing 12 i. Shafts 66 and are in vertical alignment and a universal joint broadly designated 12%, serves to opcrably interconnect opposed ends of the shafts. be lower section 13%: of joint 12S, telescoped over the upper end of shaft "125, has a pair of opposed, elongated slots i592, therein for slidably receiving opposed ends of a crosspin 134 extending through shaft 126. The upper section 136 of joint 12% is coupled direc ly to shaft for rotation therewith.

Combination pinion and ratchet members broadly numerated and Mil, are mounted on shafts es and 126 respectively, above corresponding plate portions es and ill). The member 138 carries a sleeve bearing M2 surrounding shaft 66 With a washer 14d around shaft 455 above plate portion so, serving to maintain the member 132; in predetermined spaced relationsl ip from bracket 56. The member 23% has a circumferentially extending, toothed portion 145, as well as an upper ratchet segment 148, provided with an outwardly facing, generally spiral face 15-9 having extremities interconnected by an arcuat notch 15% disposed with the outer ends thereof lying on an imaginary line passing through the axis of rotation of member 138.

A cup, broadly designated 152, is positioned on. shaft 66 in overlying complemental relationship to member 138 and includes a central boss portion 154 telescoped over shaft 66and secured thereto by a crosspin 156. The cylindrical side wall 158 of cup 152 has a notch 166 therein which clears an elongated pallet 162 rotatable about a pin 164 on side wall 166 with the inner extremity 166 of pallet 162 being disposed to slidingly engage the face 156 of member 138. Spring 168 on the outer end of pallet 162 remote from the extremity 166 thereof, is positioned to engage the adjacent portion of side wall 158 and thereby bias the extremity 166 of pallet 162 into frictional engagement with face 156.

The member 144) is similar to member 138 in that the same has a peripheral toothed portion 170, as Well as a ratchet segment 172, but as best shown in PEG. 11, the spiral face 174 thereon, although of configuration identical to that of face 156 is a mirror image of the latter. Also as shownin FIG. 11, the cup 176 overlying member 1146 and of identical construction to cup 152, is normally positioned so that the pallet 178 thereon is 180 out of phase with respect to the pallet 162. It may also be noted that the cup 176 is secured to shaft 126 by pin means 136: e I

The plate portions 66 and 62 of bracket 56, also are provided with a pair of openings 1S2 therein adjacent the outer corners thereof with the vertically spaced openings 182 being in vertical alignment to receive respective upright pins 134 which are secured thereto and project upwardly above the upper face of plate portion 66.

Idler sprockets 186 are rotatably. carried by the upper ends of pins 184 and lie in a horizontal plane passing through the toothed portion 146 of member 138. Arms, broadlydesignated 188, are mounted on each of the pins 184and extend outwardly therefrom as shown in FZGS. 2 and 4- with each arm 188 including a sleeve por- 7 tion lfi tlsurrounding corresponding pins 184 and rotatable with respect thereto between opposed plate. portions 66 and 62. Transversely polygonal support members 192 forming. a part of each of the arms 188 and project ing outwardly. from respective sleeve portions 196, have openings in the outer extremities thereof receiving a tubular bushing 194 disposed vertically and adapted to rotata-I bly receive the shaft (not shown) of a corresponding sprocket 196 Whichlie in a plane passing through idler sprockets 18-6. As illustrated in FIG. 2, an endless link chain 198 is trained around sprockets 196 on opposed arms 188 and thence over opposed sides of the idler sprockets 136 and aroundthe segment of toothed portion 146 of member 138 between idler sprockets 186. It can, therefore, be seen that upon rotation of member 138 in a clockwise direction, viewing FIG. 2, the outer sprockets 196 are rotated in a counterclockwise direction.

Means for operably coupling sprockets 196 to nuts 48 j and 50, include a pair of identical couplers broadly designated 20.0, and removably mounted on vertical bolts 202 threadedinto the bushings 194 on arms 188 and projecting upwardly above the top surface of respective sprockets 196. As shown in FIG. 4, the bolts 202 have polygonal heads normally positioned above the proximal surface of sprockets 196 with the latter being rotatable relative to corresponding bolts 202.

. The. coupler-s 200 removably mounted on the outer ends of each of the arms 188, each'include an elongated plate zlll'rotata bly carrying connector means'b-roadly designated 204 and including a lower cylindrical section 266 having a circumferentially extending toothed portion 208 thereon below the lower face of a respective plate 201. A socket section 210 is integral with the lower portion of each of the: CYl-iH-dIiCtllySECtiOnS 266, each havinga transversely polygonal recess therein adapted to be telescoped over the head of a respective bolt 262 in complemental relationship thereto. The mounting portion 212 of each connector 264 permits the cylindrical section 266, the toothed portion 268, and the socket section 216 thereof to rotate with respect to corresponding plates 261. it is tobe preferred that the mounting portion 212 be constructed in a manner so that the connector 264 may be adjusted longitudinally of a respective plate 261 for reasons to be made clear hereinafter.

' A boss 214 secured to the underside of each of the plates 291 at the extremities thereof remote from connectors 204, rotatably mount sprockets 216 which are horizontally aligned with the toothed portions 263 of proximal connectors 2M and carry relatively large socket members 218, each having a polygonal recess 226 therein adapted to be positioned over corresponding nuts 4'8 and 50. Endless chains 222 trained around the sprockets 216 and toothed portions 268 on each of the couplers 260, serve to effect rotation of socket members 216 in response to rotation of socket secti0ns210. It is to be noted that the sprockets 216, as well as the bosses 214, are of tubular configuration clearing respective screws 38 and 46 as is apparent from FIG. 2. r

Plate portions 119 and 1210f bracket 113, have vertically aligned openings adjacent opposed ends thereof for receiving elongated pins 224; positioned on opposite sides of shaft 126 and adapted to rotatably carry arms broadly designated 226 and projecting outwardly therefrom in opposite directions, as shown in FIGS. 3 and 4. Each of the arms 226 includes a sleeve portion 228 surrounding respective pins 224 and carrying laterally projecting transverseiy polygonal support members 230 which underlie arms 188 on head 24.

Tubular bushings 232 similar to bushings 194, are mounted on the outer ends of the support members 230 and rotatably carry respective sprockets 234 which are horizontally aligned with the toothed portion 170 of member 140. The bolts 236 are threaded into bushings 232 in a manner identical with the disposition of bolts 262 in bushings 194 and therefore, the heads of bolts 236 also project upwardly from sprockets 236 in order to mou t couplers 233 which are identical with couplers 200 and, therefore, will not be described in detail. However, it is to be understood that the couplers 236 of plates 240, I0- tatably mounting connectors 242 identical with connectors 264, removaby telescope over bolts 236, as well as socket members 244 positioned over the nuts 52 and 54 carried 'by screws 33 and 40. It can be recognized that chain and sprocket means also drive the socket members 244 during rotation of the connectors 242. In order to effect rotation of sprockets 234 in the same direction as sprockets 196, notwithstanding rotation of member 146 in a direct-i0 1 opposite to the direction of rotation of member 138, an endless chain 246 is trained around sprockets 234- and thence on opposite sides of the toothed portion 176 of member 146.,

A pair of idler rollers 248 are provided on opposed sides of the member and between which chain 246 must pass, in order to maintain chain 246 taut. As shown in FIG. 3, the rollers 248 rotate about vertical pins 252 ficgnnted on the upper face of plate portion 119 of bracket Pinion 74 mounted on shaft 76, has an integral, cylindrical segment 254 on the lower face thereof which carries a semicylindrical cam member 256 thereon disposed to contact the roller 258 on the switch arm 260 of a switch 262 mounted within bracket 56 (FIGS. 4 and 5).

The face of head 24 mounting bracket 56 also carries an indicator light housing 264 thereon and serving to house a pair of indicator lamps 266 and 268 which are coupled to the control unit of the present lifting apparatus by wires extending through a conduit 270 coupled to hous-. ing 264.

The electrical and hydraulicsystem of the present apparatus is illustrated diagrammatically and schematically in FIG. 10, wherein is included a pair of the housings 26d designated as 26401 and 264!) corresponding to a pair of jack units 20. It is to be understood, however, that a: housing 264 and the associated indicator lamps, are provided for each jack unit 29 utilized in a particular lifting operation. Also, in order to simplify the schematic illustration, only two cylinders 28a and 23b and associated pistons 30a and 30b, are illustrated, as well as the hydraulic motors 80a and 80b associated therewith. The consol for the present apparatus is indicated broadly by the numeral 272 and includes a hydraulic pump 274 oper y coupled to a fluid reservoir 276 by fluid line 278, as well as reversible main valve 2% coupled to the outlet of pump- 274 by a line 282, as well as the inlet of reservoir 276. by a line 284.

A pilot valve 281, similar in construction to valve 289, is hydraulically coupled in parallel with the latter by a pair of lines 283 and 285 which communicate with lines 282 and 284 respectively. The output from valve 281 is directed to opposite sides of valve 289 by lines 287 and 239 so that stem 2% of valve 280 may pe shifted by the pressure of hydraulic fluid emanating from valve 281 when the latter is shifted. A manually operable snu'bber valve 291 is disposed in line 289 to selectively regulate the rate of flow of fluid between valves 2% and 281. The stem 293 of valve 231 is operably coupled with the armatures of a pair of opposed solenoids 238 and 2% in a manner to effect reciprocation of stem 293 by the solenoids.

For purposes of the present description, a line 292 connectedto one port of valve 28b is coupled to cylinders 28a and 2812 by feeder lines 2% and 5297 respectively, while motors 83a and 8% are connected to line 292 by feeder lines 26 and 299 respectively. A second main hydraulic line 2% is coupled with the other remaining port of valve 253% and in turn is connected to the other sides of cylinders 28:: and 23b by feeder lines Sill and 3% respectively and to the other sides of motors 559a and 80b by feeder lines 298 and 365.

In the electrical schematic representation of FIG. 10, the indicator lamps 266a and 268a, corresponding to jack Zita, are illustrated in conjunction with the lamps 26617 and 26812 of the jack unit Ztib. The switch 262a associated with jack 2%, is of the double-pole, doublethrow type and thereby includes pole piece unit 3% shiftable froma central position into alternate engagement with the contacts 382 and 364, or the contacts 3% and 30%. The switch 2621) also has a pole piece unit 3%]; movable from a central position into engagement with the contacts 314 and 312 or in the alternative, contacts 314 and 316.

The contacts 362, 364, 316 and 312, as well as the filaments of lamps 266a and zssb are interposed in series relationship within a power line 313 extending from power terminal 320 to the coil of solenoid 2%, while line 322 leads from the coil of solenoid 290 to power terminal 324. The contacts 3%, 3%, 3M- and 316, as well as the filaments of lamps 268a and 268b, are also interposed in series relationship in a line 326 joining line 318 to the coil of solenoid 283. Line 328 couples the coil of solenoid 288 to line 322.

OPERATION are shown, a washer is also provided for each slot in I head 22. One jack 2% is disposed atop each building column and the number of columns will vary according to the size of each building. It is contemplated that from fifteen to thirty jacks 29 will normally be required for each lifting operation. I

Referring to the electro-hydraulic schematic diagram in FIG. 10, each jack unit 2% and 2612 has two sets of electrical switch contacts and each set is electrically coupled in series with other units of the system so that each unit forms an integral part of two different series connected electrical circuits. Also forming a necessary part of these circuits are the coils of the solenoids 288 and 290 which are located in the central control console 272. Both circuits, in turn, are connected inparallel across a source of electrical energy, as at terminals 320 and 324 so that each circuit may conduct electrical current independent of the other circuit.

In distinct contrast from the series coupling of the switch contacts of the units 24%, the hydraulic components of the units of the system are connected in parallel so that fluid is directed to the same side of the components of all of the units instantaneously. For purposes of simplification however, the hydraulic components of but two jacks 2% have been shown in FIG. 10.

The motors 89 and cylinders 23 of each jack 20, are coupled in parallel across the fluid supply lines 292 and 294 to correlate the drive of each motor 80 with the di rection of the stroke of the piston 30. Both the power means 26 and motors 86 are double-acting so that the stroke and drive is positive, with the drive being in one direction when the fluid is forced into their components through line 292 and in the opposite direction when the fluid is forced therein through line 2%.

Pump 274 is operably coupled to a motor (not shown) and maintains the fluid which is supplied from reservoir 276 at a predetermined pressure. the coils of solenoids 288 and 290 through the electrical circuits which include the electrical components of each unit Ztl, will be explained in greater detail hereinafter.

On the initial lifting stroke of the system, pressurized fluid is directed into one side of cylinder 28 from line 292. This forces piston 30 upward which in turn raises head 24. The nuts 48 and St threadably disposed on screws 33 and 4%), cause the latter to be lifted byhead 24. The load fastened to the screws is also lifted. Head 22 remains stationary and nuts 52 and 54, engaging screws 38 and 40 above head 22, are raised off the latter an amount equal to the stroke of cylinder 30.

The stroke cylinder 23 is relatively short and is calculated to be less than the maximum deflection which can be tolerated by the slab which is being lifted. In other words, the stroke of the cylinder is such that if some of the jacks lifted the slab the full amount of the stroke, and others, for one reason or another, did not displace the load at all, the bending imparted to the slab from such unequal displacement on one stroke would be with ing the flexure tolerance of the slab. Obviously, the stroke length could be varied from slab to slab, but it has been found that a stroke of one-half inch is well suited for most lifting operations.

Referring now to FIGS. 6 and 10, as hydraulic fluid is directed through line 292 into one side of cylinder 28 to raise piston 30, it is simultaneously directed into passage 108 of motor 80. Fluid entering passage 108 flows through bore 104 and into passage 84 where it acts against end 98a, forcing piston 98 toward end section 86. Ac-

cordingly, fluid entering passage 108 is also permitted to fiow'through passage 116 where it acts against end 96b, forcing cylinder 96 toward end section 88. The resultant shifting of cylinders 96 and 98 in opposite directions causes pinion 92 in bore 99 of motor to be engaged by the rack portions of cylinders 96 and 98 and to be rotated in a counterclockwise direction as viewed in FIGS. Sand 6. The maximum amount of rotation possible for pinion 92 is 360.

Manifestly, shaft 76, rigidly coupled to pinion 92, is-

also driven in a counterclockwise direction. Shaft 76 turns pinion 74, thereby driving pinion 72 in a clockwise direction as viewed in FIG. 5. Shaft 66, rigidly coupled to pinion 72, is likewise driven in a clockwise direction.

The energization of The respective sizes of pinions 72 and 74 are preferably calculated to drive pinion 72, 2% revolutions for each revolution of pinion 74. Inasmuch as pinion 92 may only be driven one full revolution before cylinders 96 and 98 reach their extreme positions, shaft 66 can only be revolved a maximum of 2% times each time fluid is directed to one side of motor 80.

The rotation of shaft 66 in a clockwise direction, causes cups 152 and 176 rigid to shaft 66 and carrying pallets 162 and 178 respectively, to likewise be rotated in a clockwise direction. As will clearly appear from FIG. 11, which shows a starting position of the pallets with respect to the segments, pallet 178 is not initially in a position to engage notch 150a of segment 172 and also, clockwise rotation of pallet 162 will not cause pallet 162 to engage notch 156a of segment 148 because of the circumferential configuration of the latter. As viewed in FIG. 12, after such clockwise rotation has proceeded a predetermined amount however, pallet 178 moves into engagement with notch 150a of segment 172 and drives the latter in a clockwise direction.

It is clear, therefore, that such clockwise rotation of segment 172 and its integral toothed portion 170, drives chain 246 clockwise as viewed in FIG. 3, and in turn opcrates couplers 238 which rotate nuts 52 and 54 in the same direction, thereby threading them toward engagement on washers 46 overlying head 22. Inasmuch as the rotation of pallet 162 in a clockwise direction cannot drive segment 148, and it slides along edge 150 thereof, no driving force is imparted to chain 198 and, therefore, the couplers 200 are not driven. It should be pointed out at this juncture that the fluid is directed into motor 80 at the same time that it is directed into cylinder 28 so that nuts 52 and 54 are moved down their respective screws as the load is being lifted. Thus, in the event of a break in the hydraulic line or the like, the load would not be dropped because of spacing between the nuts and the supporting head 22. At the end of the lift stroke, the assembly is ready to withdraw head 24 to obtain a new bite for lifting the load another increment. The relative position of the pallets and segments at this time is shown in FIG. 13.

Through appropriate switching means to be explained in detail later, stem 286 of valve 280 is shifted at this time to reverse the direction of flow of fluid through the hydraulic line. The forcing of fluid into the opposite side of cylinder 28 through line 294, retracts piston 30. Simultaneously, fluid from line 298 is directed into passage 106 of motor 128, driving cylinders 96 and 98 in the opposite direction from the direction of drive when fluid enters through passage 108. This rotates shaft 76 in a clockwise direction as viewed in FIGS. 5 and 6, resulting in the rotation of shaft 66 in a counterclockwise direction as viewed in FIGS. 5 and 8. As is apparent from viewing FIG. 14, pallet 178, rotating counterclockwise, cannot engage notch 1511a of segment 172 to drive the latter because of the peripheral configuration of the segment. Instead, the pallet slides along edge 150 of the segment. Pallet 162 is initially not in driving engagement with segment 148, but after a predetermined amount of lost rotation, pallet 162 engages notch 150a of segment 148 and drives the latter counterclockwise as shown in FIG. 15. Due to the disposition of chain 198 with respect to toothed portion 146 of ratchet means 138, as shown in FIG. 2, chain 198 is driven in a clockwise direction notwithstanding the fact that segment 148 rotates counterclockwise as viewed in FIG. 2. Chain 198 operates the couplers 200, therebythreading nuts 48 and 50 down toward head 24 as the latter is withdrawn from nuts 48 and 50 by action of the fluid on piston 30. Heads 22 and 24, and nuts 48, 50, 52 and 54, are now in position for another lift stroke as shown in FIG. 16.

With head 24 again in its retracted position, a full cycle has been completed with piston 30 having lifted screws 38 and 40the amount of its stroke, nuts 52 and 54 having been threaded down screws 38 and '40 to engage head 22 for holding the load, head 24 having withdrawn for a new bite and nuts 48 and 50 having been threaded down screws 38 and 40 to closely overlie head 24 in preparation for the next succeeding stroke. It should be pointed out that cups 152 and 176 are operably coupled together at all times by shafts 66, universal joint 138 and shaft 126, and that pallets 162 and 1'78 rotate together with shaft 66and shaft 126 respectively.

Referring to FIG. 10, the electrical circuits are so arranged that when a plurality of jacks 20 are interconnected in series, the indicator lights 266 of all jacks and solenoid 290 of the control console 272 areelectricallycoupled in series in one electrical circuit. Also, the light 268 are all coupled in series with solenoid 288 in a second circuit. Accordingly, if electricity flows through either circuit, energy will be supplied to the respective lights 266- or 268 and they will be illuminated. The resistances of the respective lights are such, when added to the resistance of the solenoid coil 288 or 290 in each series circuit, that not enough electricity to energize the coil will flow through the respective circuit while even one light is connected in the circuit in series with the coil. However, when the pole pieces 3% of the respective switches on all of the units 20 (only switches 262a and 26212 are illustrated) are shifted into shunting position across the contacts on either side of the lights, the pole pieces 300 shunt the electrical current through a path of diminished resistance and the lights are eflfectively removed from the circuits by the shunt. This shunting effect by the pole pieces 300 keep the lights extinguished. The very low resistance of these switches permits sufiicient flow of electricity through the circuit to energize the respective coil in that circuit.

It will be noted, that when pole pieces 360a and 3116b are in shunting position in one circuit, they are withdrawn from a shunting position in the other circuit.

Therefore, sufiicient electricity to operate a solenoid can flow in only one circuit at any given time. When pole piece 3416a is in position bridging contacts 302 and 3114, and pole piece 3110b is bridging contacts 310 and 312, lights 266a and 266b are extinguished and solenoid coil 296) is energized. Accordingly, when pole piece 300a bridges contacts 366 and 3418, and pole piece 360]; bridges contacts 314 and 316, lights 268a and 268b are extinguished and coil 288 is energized. It will be readily apparent that although only the switches 262 of two jack units 20 have been shown, what has been said with respect to switches 262a and 2621? applies equally to the switches 262 of all of the units 20 of the system. Each pole piece 3% of switches 262 has an intermediate position out of contact with either circuit, which position is illustrated in FIG. 10. Switch 262 is mechanically coupled to shaft 76 through arm 266, roller 258 and cam member 256 so that upon each rotation of shaft 76, arrn 260 is shifted, thereby withdrawing pole piece 300 of switch 262 from its initial shunting position in one electrical circuit and, if the rotation of shaft 76 is sufficient, installing it into its alternate shunting position in the other electrical circuit. If, for some reason, such as failure of piston 36 to advance the load a sufficient amount, shaft76 is prevented from rotating its requisite angular amount, pole piece 300 of switch 262 will not be shifted to a shunting position, but will remain in its intermediate position. This will allow a fiow of electricity through that circuit, but such flow, due to the resistance of the indicator light that is not shuned out by pole piece 30 will not be sufiicient to adequately energize the solenoid coil in that circuit. Therefore, stem 286 of valve 286 will not be shifted, and no further hydraulic fluid will be provided to unit 21) to reverse motor 80 and piston 36. Thus, the switches 262 comprise components for rendering the prime mover inoperable upon failure of the unit to function properly.

Inasmuch as all units 26 of the system are electrically coupled in series, all. will. be rendered inoperative for lack of sufficient electrical power upon the failure of one thereof to displace the load its predetermined necessary dismore than one unit has failed to lift its load the required increment, each such unit will have an illuminated indicator light. Although the lights in the other circuit do not have pole pieces shunted across their respective contacts, additive resistances of substantially all of the lights, plus that of the coil of the solenoid in that circuit, are sufficientto prevent a flow of electricity through the second circuit, thereby preventing the indicator lights from illuminating. The operator then can not only tell which units have failed to operate properly, but also whether such failure occurred on the lift stroke or the return stroke. This, of course, is indicated by whether light 266 or sea is illuminated.

In the past, much difficulty has been encountered with jacks utilized for erecting buildings because various factors affected the amount of load displacement of each jack.

If a predetermined amount was set for the take-up of the respective nuts, any variation in the distance which the load was moved would cause the nuts to jam upon the heads and stop the effective operation of the jack.

The unique design of jack unit 20, including the ratchet and palletarrangement, allows for a pre-set tolerance to be taken into consideration to prevent such stoppages. Variations in the lift increment, falling within this tolerance, will not prevent this unit from operating. t the same time, should any jack in the system fail to displace the load an amount not Within the tolerable limits, the entire system is rendered ineffective until such deflection differential has been eliminated. This is, of course, necessary to prevent damage to the loads, which are often concrete slabs of very large dimensions and incapable of withstanding stresses caused by uneven lifting.

The arrangement of the two driving pallets 162 and 178 with the driven segments 148 and 172, is such that a particular angular displacement of the pallets is transmitted into a corresponding linear displacement of nuts 48, 52 and 50, 54 along respective screws 38 and 40. By providing for certain lost angular motion between the pallets and the segments, specific linear tolerance in the take-up of the respective nuts, is maintained.

It has been found desirable to have the threads of screws 38 and 40 pitched so that one revolution of a nut thereon is equivalent to /4 of an inch linear displacement along the screw. A stroke of /8 inch for piston 30 has been found to be adequate for most lifting operations and will be used as a basis for this explanation. Also, it has been found desirable to have nuts and 50 spaced of an inch above head 24 prior to the lift stroke of piston 30. This spacing allows for deflection in the beams themselves when loaded, inadvertent variations in thread sizes on screws 30 and d0, differences in the weight lifted by each unit due to its position with respect to the load, and other variations previously referred to. With this spacing of A3 of one inch between the upper nuts and the head, the load is lifted only /2 of one inch for a full stroke of /s inch of the piston 30.

In order to begin operation with unit 20, nuts d8 and 50 are threaded to a position overlying head 24, with the exact spacing therefrom not critical inasmuch as the machine will automatically pick up a uniform inch spacing and maintain that spacing throughout operation. It will be understood, however, that this initial spacing should be somewhere between 0 to /4 of one inch for the particular screws 30 and 40 described. For illustration, assume that nuts 48 and 50 are initially spaced of one inch from head 24'.

If the pallets res and 173 are disposed relative to the respective segments 14-8 and 172 in the positions shown in PEG. 11, pallet 1.78 will rotate 180 clockwise, as viewed in FIGS. 11-16, before engaging notch 150:: of segment 172 on the lift stroke.

Inasmuch as shaft 66 rotates a maximum of 2% times or 990 for each stroke of motor as previously described, pallet 178 will likewise rotate a maximum of 990. Because 180 of this is lost rotation, segment 172 will be driven only a total of 810. This is equivalent to W inch linear distance on screws 38 and 40. a

At this point, illustrated schematically in FIG. 13, the hydro-electric circuit is reversed due to the shifting of .the switches 262 and motor oil operates in the reverse direction. Pallet 162 must rotate 270 before it engages notch of segment 1 2-8. Accordingly, on this counterclockwise rotation, pallet 17% will be ineffective to drive segment 172 because of the peripheral configuration of the latter. After a rotation of 270, pallet 162 picks up segment 148 as shown schematically in FIG. 14. At the same time, piston 3:0 is withdrawn into cylinder 28, thereby retracting head 24 from engagement with nuts 48 and 50 as shown. Pallet 1162 is driven a full 990 in the counterclockwise direction, but segment 148 is only driven 990 minus the last 270, or a total of 720 which is equivalent to /2 inch linear distance on screws 38 and 4-0. I

The positions of the respective components at the end of this stroke, are illustrated schematically in FIG. 15. It thus appears that the rotation of the lower segment 172 has amounted to 810 or A of one inch, whereas, the effective rotation of segment 14% has been 720, or A2 of one inch. This differenceof of an inch means that nuts and 50 have not been displaced downwardly on screws 38 and 40 so far by that amount as have nuts 52 and 5a. This has resulted, of course, from the lost motion between the pallets and segments and a spacing of A; of an inch has now been established between the upper nuts and upper head.

FIG. 16 shows the relative positions of the pallets 1.62 and 178 when pallet 178 is again in position to engage notch 152a of segment 172 to drive the latter. It will be noted that the positions of the pallets with their respecive segments differ in FIG. 16 from FIG. 12 in that segment 172 and pallet 178 have rotated an additional 90 before the driving engagement commences. Also, pallet 162 is 90 closer to driving engagement with segment 148. Consequently, the relative positions of the segments and pallets have automatically become so aligned that any further take-up on screws 38 .and 40 will bring nuts 48 and 50 to within A; of one inch from engagement with head 24. This is brought about by the fact that segment 172 will be effectively driven 720, or the equivalent of /2 of one inch linear displacement on each takeup cycle, leaving the pallet 152m position to have 270 lost rotation before the latter engages notch 1.50:: of segment 148. This differential, in effective rotation, is maintained throughout the operation of unit 20.

Now assume, for purposes of explanation, that the upper nuts are initially spaced /4 inch above head 2 Since the stroke of piston 30 is /3 inch and head 24 must be lifted inch before it engages nuts 48 and 50, the load will only be lifted a total of inch on the initial lift stroke. Thus, lower nuts 52 and 5 may only be turned down inch before they bottom out snug against head 22, thereby stalling motor 80. This linear distance of inch is equivalent to 540 so ratchet 172 may only be turned that amount before stalling occurs. However, pallet 173 has of free travel before it initially picks up itn ratchet 172 (PEG. 11) so motor 80 may operate as if it had turned the nuts 720 before stalling. Thus, the pallets 1'78 and 162 are turned two full revolutions from their starting position when the reversal of the hydraulic fluid occurs and are in the same relative positions, when the take-up strokebegins as they were initially (shown in FIG. 11). It may be readily seen that this leaves pallet 162 in position to drive ratchet 148 Without lost motion, when the clockwise rotation on the take-up stroke begins. Motor 8%) has .stalled before completing its previous stroke so it may drive in the reverse direction on the take-up stroke an amount equal to the drive on the previous stroke. Since this amount is equivalent to 720 and there is no lost motion between the rotation of pallet 162 and the drive of nuts 48 and 56 because of the relative positions between pallet 162 and ratchet 148 at the beginning of this stroke, the nuts are threated down the screws 720 or /2 inch. Head 24 is withdrawn the full amount of the stroke which is /8 inch. Thus, a spacing of /8 minus /2, or a total of A; inch has been established between the upper nuts and the upper head. Similarly, a spacing of /8 inch will be automatically picked up whenever the initial spacing is between inch. This discussion presupposes, however, that the hydraulic system would be reversed if motor 8t failed to complete its initial stroke. Such reversal would have to be done manually on the first stroke because of the failure of switch 262 to complete the solenoid energizing circuit as previously explained.

Were it not for this tolerance of A; of one inch, minor variations in load displacement would stop the unit 2t? because nuts 48 and would be required to displace linearly an amount precisely equal to the amount of load lift. Any minor variation in this displacement would not let this be possible, and the electrical components would halt the lifting operation until precise equality of stroke could be established. Such precision is not necessary. It is sufficient if such variations be kept within /a inch which is not sufiicient to cause damage to the slab; whenever the variations exceed this amount, the lifting is automatically halted.

Although the various jacks of the system are operably intercoupled so that all jacks are in the same stroke at the same time, there is no attempt to have all jacks in precisely the same phase of a given stroke at the same time. ()bviously, the speed of lift of the various jacks will depend upon the amount of weight lifted by a particular jack. Those near the edge, for example, would be expected to displace the load more quickly than those near the center of the slab. The build-up of hydraulic pressure to its maximum value does not occur until near the end of any particular stroke and near peak pressure is required by some of the jacks for lifting the load, while others will not need such pressure. Since the direction of flow of hydraulic fluid would not be reversed until the very last switch 262 had been shifted, all of the other jacks of the system will be provided with hydraulic pressure even after their switches have been shifted. Thus they get the benefit of such pressure build-up occurring near the end of the stroke, to provide those that need it the relatively short interval of maximum pressure application to cause them to displace the load the slight increment which may be necessary to achieve maximum stroke. When the last switch 252 of the system is shifted, however, there would be instant reversal of the flow of fluid unless provision were made for a time delay between switch shifting and the shifting of valve 239. Such immediate reversal of fluid would deprive the last jack, the one having the heaviest burden, of the benefit of the. build-up of pressure for lifting the last small increment of the stroke. A variable delay in the reversal of fluid flow after the electrical components sense that all jacks have lifted their load is provided by the pilot valve 281. The shifting of valve 281 by the solenoids, reverses the flow through the valve and directs fluid pressure against one or the other of the ends of main valve 280, causing the latter to be shifted. The direction of flow of hydraulic fluid supplied to the respective jacks will not be reversed until main valve 289 is shifted. The speed of such shifting may be controlled by snubber valve 291 disposed in line 289. Closing down of the valve to id restrict the flow of fluid to main valve 28%, slows the shifting of the latter, while opening of valve 291 speeds up the shifting process. The amount of the delay in the shifting of the main valve following the closing of all of the switches can be selectively adjusted to provide the very last jack with the required fluid pressure.

The delay built into the system provides the last jack with the required pressure for lifting the last increment of distance. It is desirable that the lower nuts 52 and 54- bottom out each time against their seats to prevent shock to the slab when the jacks start their retraction cycle, at which time the load is transferred from the up per nuts to the lower nuts. Recognizing that such bottoming out will occur at various stages during the last increment of lift and during the period of delay, it is desirable that minor variations in the time at which motor 8% is stalled thereby not prevent the automatic cycling of the jack. Such minor variations may occur from slight variations in the pitch of the rod thread, trash on the nut seat or rod thread, or the like. Therefore, means is provided for causing the electrical components to sense that all of the pistons 3d are fully extended even though the lifting is not quite completed. Referring to FIG. 5, segment 254 is provided with cam member 2&5 extending preferably 35 around its peripheral edge. Thus, arm 26% and consequently, switch 262, is shifted approximately 35 before shaft 76, rigid to segment 254, is rotated a full turn on the lift stroke. This means that all lights are extinguished and solenoid 23 8 energized to begin the delayed shifting process even though the bottom nuts may perhaps yet be turned of an inch.

A further factor affecting slab impact or shock is the speed with which the stem of the main valve 28% is shifted. Too rapid shifting increases the impact on the slab and may damage the latter. Snubber valve 2% may be adjusted to control this speed and therefore, comprises means for minimizing the shock of the transfer of the load from the upper to the lower head. Adjustment of the snubber valve 291 to dimish the rate of flow of fluidthrough line 289, will smooth out the shifting of the slab from head 24- to head 22 and the operator can tell from the feel of the slab as he stands thereon during the lifting process, when the adjustment is proper.

Viewing FIG. 7, it may readily be seen that plate Ztll is rigid and that the distance between toothed portion 2&8 and sprocket 216 of couplers 2%, as well as couplers 238, will remain constant. When various sized columns are used in the building, it may be necessary to vary the distance between the screws 38 and 4E? with one screw preferably disposed on each side of the column. This may be accomplished because heads 22 and 24 are provided with elongated slots 34 and 36. Since the couplers 26d and 238 have fixed radii, there will be no slackening of the driving chains 198 or 246 when the distance between the screws 38 and 40 is varied. The tension in chains 1% and 245 is further preserved by arms 188 and 22d, maintaining sprockets 196 and 234 spaced uniformly from their respective axes of rotation, pins 184 and 224, despite swinging movement of the arms to compensate for variable spacing of screws 38 and 49.

In the event that the jack unit 21) is rendered inoperative because of failure of any of the nuts to displace the required amount, and after correcting the cause, it is a simple matter for the operator, who has been directed to the proper unit by its indicator light, to slide the re: cesses 226 off the nuts 48 and 59 or 52 and 54, thereby sliding the socket sections 21! off of the respective bolts 292 or 2%. This breaks the drive between the corresponding segment 1 58 or 172 to the respective nuts and allows the segments to be properly aligned in preparation for following stroke. Such alignment may be facilitated by suitable aligning indices disposed to reveal the position of the ratchets 143 and 172. When once more in proper alignment, jack 20 is again ready for operation. The couplers 209 or 258 are returned to their operating positions in operable engagement with their respective nuts and bolts 2% or 236.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. in a lifting structure, the combination of a jack unit provided with an upper and a lower head; means supporting the lower head; a pair of spaced, upright screws extending through the heads and coupled with a load to be lifted; power means between the heads having vertically reciprocable means for raising the upper head; a pair of upper nuts, one on each screw respectively above the upper head, through which the screws and load are lifted while the upper head is raised; a pair of lower nuts, one on each screw respectively above the lower head, through which the latter supports the screws and load while the upper head descends; a first mechanism connected with the lower nuts for lowering the latter following the commencement of each step of ascent of the upper head; a second mechanism connected with the upper nuts for lowering the latter following the commencement of each step of descent of the upper head; a prime mover for actuating said mechanisms, said prime mover being provided with a drive movable alternately in opposite directions; apparatus coupling the drive with the first mechanism for actuating the latter when the drive moves in one direction; and apparatus coupling the drive with the second mechanism for actuating the latter when the drive moves in the opposite direction.

Z. The invention of claim 1, and a control operably coupled with the prime mover for limiting the extent of movement of said drive in both directions.

3. The invention of claim 2, said control being pro vided with means for reversing the drive following movement thereof to each end of its path of travel.

4. The invention of claim 3, said reversing means having components for rendering the prime mover inoperable upon failure of said nuts to descend at least a predetermined distance during any actuation of corresponding mechanisms.

5. The invention of claim 1, said drive being rotatable, each apparatus including a movable pallet carried by the drive for rotation therewith and a pallet-actuated ratchet element operably coupled with a corresponding mechanism, one of the pallets engaging its element and the other pallet moving past its element when the drive is rotated in one direction, the other pallet engaging its element and the one pallet moving past its element when the drive is rotated in the opposite direction.

6. The invention of claim 5, there being a sprocket wheel for each element respectively rotatable therewith on said drive, each mechanism including a primary chain in mesh with a corresponding wheel.

7. The invention of claim 6, said heads having screw clearance means, thereby permitting variance in the distance between the screws, there being a pair of idlers in mesh with each chain respectively, each mechanism inluding a secondary chain operably connecting each nut with a corresponding idler, and means supporting each idler respectively for swinging movement, whereby the primary chains remain taut throughout variances in the distance between the screws.

8. In a lifting structure, the combination of a jack unit provided with an upper and a lower head; means supporting the lower head; a pair of spaced, upright screws extending through the heads and coupledrwith a load to be lifted; power means between the heads having vertically reciprocable means for raising the upper head; a pair of upper nuts, one on each screw respectively above the upper head, through which the screws and load are lifted while the upper head is raised; a pair of lower nuts, one on each screw respectively above the lower head, through which the latter supports the screws and load while the upper head descends; a first mechanism connected with the lower nuts for lowering the latter followtill ing the commencement of each step of ascent of the upper head; a second mechanism connected with th upper nuts for lowering the latter following the commencement of each step of descent of the upper head; a prime rover for actuating said mechanisms, said prime mover being provided with a reversible power shaft; a one-way ratchet pallet drive for each mechanism respectively; means for each of the pallets of the'drives respectively operably coupling the same with the shaft for rotation of both pallets during each rotative movement of the shaft in either direction; apparatus coupling the ratchet of each drive with a corresponding mechanism, each ratchet having a single pallet-engaging tooth, there being a ratio of rotation between the shaft and the nuts to present a lost motion in each drive during each cycle of nut movement whereby to compensate for bending stresses in the heads resulting from the weight of said load thereon.

9. The invention of claim 8, there being speed-increase means between the shaft and said pallets whereby, during each revolution of the shaft in either direction, the pallets rotate simultaneously more than one revolution, thereby presenting said ratio of rotation.

1d. Apparatus for lifting monolithic building slabs comprising a plurality of jack units each having an upper and a lower head; means supporting each of the lower heads in horizontally spaced relationship; a pair of spaced, upright screws extending through each of the heads and adapted to be coupled to the slab in spaced relationship; fluid-actuated power means between the heads of each unit for having vertically reciprocable means for raising corresponding upper heads with respect to the lower heads therebelow; a pair of upper nuts for each jack unit respectively, one on each screw respectively associated with a corresponding jack unit and located above the upper head thereon, through which the screws and the slab are lifted while the upper heads are raised; a pair of lower nuts for each jack unit respectively, one on each screw respectively associated with a corresponding jack unit and located above the lower head thereon, through which the latter support the screws and load while corresponding upper nuts descend; a first mechanism connected with the lower nuts of each jack unit for lowering corresponding lower nuts following the commencement of each step of the ascent of respective upper heads; a second mechanism connected with the upper nuts of each jack unit for lowering corresponding upper nuts following the commencement of each step of descent of respective upper heads; a fluid-operated prime mover on each unit for actuating the mechanisms thereon, each of said prime movers being provided with a drive movable alternately in opposite directions; apparatus on each jack unit coupling a corresponding drive with the first mechanism thereon for actuating the latter when the drive of each apparatus moves in one direction; apparatus on each jack unit coupling the drive thereon with a respective second mechanism on the same for actuating corresponding second mechanisms when respective drives move in a direction opposite to said one direction; means for supplying fluid under pressure to said power means and said prime mover; fluid control means operably coupled with said power means for actuating the latter through a period of effect raising the upper head of each unit relative to the lower head thereon, and correlated with the force applied to the slab by the jack units for causing the slab to be lifted through successive increments less than the maximum deflection that can be tolerated by the slab; and electrically actuated means operably associated with the prime mover of each jack unit for sensing the amount of movement of corresponding drives in said one direction thereof to deactivate said control means if any of the power means should fail to lift corresponding upper heads through the normal increment of upper movement thereof.

11. Apparatus as set forth in claim 10, wherein each jack unit is provided with a shaft operably coupled with the drive thereof for rotation by the latter, a cam member carried by each shaft for rotation therewith, a normally open electrical switch for each jack unit, regulating means operably coupled with and common to the power means for controlling flow of fluid to the same, said regulating means including a valve and a solenoid operably coupled with the valve, solenoid energizing circuit means electrically coupling the switches in series with the solenoid and adapted to be coupled with a source of electrical energy, and a switch arm operably coupled with each switch and disposed to be engaged by corresponding cams on said shafts to effect the operation of a respective switch when a respective shaft is rotated through a predetermined arc whereby said solenoid energizing circuit is closed only upon the rotation of all of the shafts a predetermined amount by their respective drives 12. Apparatus as set' forth in claim 11, wherein an electric lamp is electrically coupled in series across the contacts of each switch.

13. Apparatus as set forth in claim 12, wherein each switch is provided with a pole piece shiftable to a position bridging the contacts of the switch when the latter is operated, said pole piece being of appreciably lesser resistance than a corresponding lamp whereby the flow of electrical energy is shunted around the lamp when said switch is in its operated condition.

14. Apparatus as set forth in claim 13, wherein the additive resistance of the solenoid and all of the lamps is sufficient to prevent any fiow of electricity through the circuit and the additive resistance of the solenoid and at least one lamp 'is sufiicient to prevent the energizing of the solenoid but insufiicient to prevent the energizing of the lamps whereby failure of the drives of any of the jack units to rotate their respective shafts through an are great enough to operate their respective switches, is signalled by the illuminating of the lamps of those particular jack units.

15. For use in connection with a slab of the type which has a maximum deflection tolerance, structure for lifting said slab along a plurality of spaced uprights without damaging the slab incident to deflection thereof as the result of application of lifting forces to the slab at each of said uprights, said structure including:

lifting apparatus for each upright respectively,

each apparatus including a first head adapted to be carried by a corresponding upright,

a second head spaced vertically from the first head,

a jack between the heads for reciprocating the second head vertically toward and away from the first head, said jack provided with a vertically reciprocable power unit having a predetermined lifting stroke,

a carrier adapted for connection with the slab,

first take-up means on the carrier in overlying engagement with the first head and in supporting relationship to the slab while the second head is being lowered by the unit, second take-up means on the carrier in overlying engagement with the second head and in supporting relationship to the slab while the unit is raising the slab, jack operating means coupled with the jack for raising said second head to the full limit of said lifting stroke of the unit, and actuating means coupled with said take-up means and including a first mechanism for lowering said first take-up means during each upward movement of the second head, and a second mechanism for lowering the second take-up means during each downward movement of the second head, said second mechanism being operable upon each actuation thereof to move said second take-up means a preselected fixed distance,

said distance being less than the extent of downward movement of said second head whereby the extent of slab raising during each cycle of reciprocation of the unit is limited to said preselected distance.

16. The invention of claim 15, reversing: means operably coupled with said jack operating means for controlling reciprocation of the jack; means operably interconnecting said mechanisms and said reversing means for actuating the latter upon full lowering of the take-up means.

17. The invention of claim 16, and safety means operably coupled with said interconnecting means for deactivating the reversing means in absence of full lowering of the take-up means.

References Qited by the Examiner UNITED STATES PATENTS 1,500,859 7/24 Wright 25492 1,994,087 3/35 Onstad 50-534 2,472,221 6/49 Malthouse 50534 2,530,807 11/50 Campbell 354-92 2,732,177 1/56 Ludowici 5080 2,758,467 8/56 Brown et al 5080 2,942,848 6/60 Friesen 254894 2,947,148 8/60 Young 254-410 2,963,868 12/60 Armstrong 254-405 3,028,143 4/62 Cheskin 50-80 3,036,816 5/62 Stubbs et al. 254 3,053,015 9/62 Graham 50-80 X WILLIAM FELDMAN, Primary Examiner.

JACOB L. NACKENOFF, MILTON S. MEI-IR,

Examiners. 

1. IN A LIFTING STRUCTURE, THE COMBINATION OF A JACK UNIT PROVIDED WITH AN UPPER AND A LOWER HEAD; MEAND SUPPORTING THE LOWER HEAD; A PAIR OF SPACED, UPRIGHT SCREWS EXTENDING THROUGH THE HEADS AND COUPLED WITH A LOAD TO BE LIFTED; POWER MEAND BETWEEN THE HEADS HAVING VERTICALLY RECIPROCABLE MEAND FOR RAISING THE UPPER HEAD; A PAIR OF UPPER NUTS, ONE ON EACH SCREW RESPECTIVELY ABOVE THE UPPER HEAD, THROUGH WHICH THE SCREWS AND LOAD ARE LIFTED WHILE THE UPPER HEAD IS RAISED; A PAIR OF LOWER NUTS, ONE ON EACH SCREW RESPECTIVELY ABOVE THE LOWER HEAD, THROUGH WHICH THE LATTER SUPPORTS THE SCREWS AND LOAD WHILE THE UPPER HEAD DESCENDS; A FIRST MECHANISM CONNECTED WITH THE LOWER NUTS FOR LOWERING THE LATTER FOLLOWING THE COMMENCEMENT OF EACH STEP OF ASCENT OF THE UPPER HEAD; A SECOND MECHANISM CONNECTED WITH THE UPPER NUTS FOR LOWERING THE LATTER FOLLOWING THE COMMENCEMENT OF EACH STEP OF DESCENT OF THE UPPER HEAD; A PRIME MOVER FOR ACTUATING SAID MECHANISMS, SAID PRIME MOVER BEING PROVIDED WITH A DRIVE MOVABLE ALTERNATELY IN OPPOSITE DIRECTIONS; APPARATUS COUPLING THE DRIVE WITH THE FIRST MECHANISM FOR ACTUATING THE LATTER WHEN THE DRIVE MOVES IN ONE DIRECTION; AND APPARATUS COUPLING THE DRIVE WITH THE SECOND MECHANISM FOR ACTUATING THE LATTER WHEN THE DRIVE MOVES IN THE OPPOSITE DIRECTION. 